Ascl2 knockdown results in tumor growth arrest by miRNA-302b-related inhibition of colon cancer progenitor cells

• Published in: PloS one 2012-02, Vol.7 (2), p.e32170-e32170
• Main Authors: Zhu, Rong, Yang, Yongtao, Tian, Yin, Bai, Jianying, Zhang, Xin, Li, Xiaohuan, Peng, Zhihong, He, Yonghong, Chen, Lei, Pan, Qiong, Fang, Dianchun, Chen, Wensheng, Qian, Chen, Bian, Xiuwu, Wang, Rongquan
• Format: Article
• Language: English
• Subjects: AC133 Antigen; Adenocarcinoma; Animals; Antigens, CD - biosynthesis; Basic Helix-Loop-Helix Transcription Factors - metabolism; Biology; Breast cancer; c-Myc protein; Cancer; Cancer genetics; Cancer prevention; Cell cycle; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cells (biology); Colon; Colon cancer; Colonic Neoplasms - metabolism; Colonies; Colorectal cancer; DNA microarrays; Fibroblasts; Forming; Gastroenterology; Gene expression; Genes; Genetic aspects; Glycoproteins - biosynthesis; Growth; Helix-loop-helix proteins; Helix-loop-helix proteins (basic); Humans; Immunohistochemistry; Inhibition; Interference; Intestine; Male; Medical research; Medicine; Mice; Mice, Inbred BALB C; Mice, Nude; MicroRNA; MicroRNAs; MicroRNAs - metabolism; miRNA; Myc protein; Neoplasm Invasiveness; Neoplasm Transplantation; Oct-4 protein; Peptides; Progenitor cells; Restoration; Ribonucleic acid; RNA; RNA Interference; RNA-mediated interference; Stem cells; Stem Cells - cytology; Transcription factors; Tumors; Xenografts; Xenotransplantation
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0032170

Achaete scute-like 2 (Ascl2), a basic helix-loop-helix (bHLH) transcription factor, controls the fate of intestinal stem cells. However, the role of Ascl2 in colon cancer progenitor cells remains unknown. The cell line HT-29 (47.5-95% of CD133(+) population) and LS174T (0.45% of CD133(+) population) were chosen for functional evaluation of Ascl2 in colon cancer progenitor cells after gene knockdown by RNA interference. Immunohistochemistry demonstrated that Ascl2 was significantly increased in colorectal adenocarcinomas. Downregulation of Ascl2 using RNA interference in cultured colonic adenocarcinoma HT-29 and LS174T cells reduced cellular proliferation, colony-forming ability, invasion and migration in vitro, and resulted in the growth arrest of tumor xenografts in vivo. The Ascl2 protein level in CD133(+) HT-29 cells was significantly higher than in CD133(-) HT-29 cells. Ascl2 blockade via shRNA interference in HT-29 cells (shRNA-Ascl2/HT-29 cells) resulted in 26.2% of cells staining CD133(+) compared with 54.7% in control shRNA-Ctr/HT-29 cells. The levels of 'stemness' associated genes, such as CD133, Sox2, Oct4, Lgr5, Bmi1, and C-myc, were significantly decreased in shRNA-Ascl2/HT-29 and shRNA-Ascl2/LS174T cells in vitro as well as in the corresponding tumor xenograft (CD133 was not performed in shRNA-Ascl2/LS174T cells). The shRNA-Ascl2/HT-29 cells had inhibited abilities to form tumorspheres compared with control. The microRNA (miRNAs) microarrays, identified 26 up-regulated miRNAs and 58 down-regulated miRNAs in shRNA-Ascl2/HT-29 cells. Expression levels of let-7b, miRNA-124, miRNA-125b, miRNA-17, miRNA-20a and miRNA-302b, involved in the regulation of 'stemness', were quantified with qPCR, which confirmed their identities. Restoration of miRNA-302b, via its mimic, led to the restoration of shRNA-Ascl2/HT-29 'stemness' characteristics, including tumorsphere formation and 'stemness' associated genes levels, and the recovery of cellular behaviors, including colony-forming ability, invasion and migration in vitro. Ascl2 may be a potential target for the inhibition of colon cancer progenitor cells, and functions through a miR-302b-related mechanism.